Ultrafast Nondiffacting Optics and Ultrafast Singular Opticsopen
new prospects for the study of fundamental problems of optical
physics as well as future applications. For the spatio-temporal shaping
and diagnosing few-cycle wavepackets, in particular for the flexible
generation of nondiffracting pulses and pulses with orbital angular
momentum (OAM), liquid-crystal-on-siilicon spatial light modulators
(LCoS-SLMs) and novel types of tunable reflective components are
applied. Low-dispersion mirrors and spiral phase plates for few-cycle
laser applications are developed and characterized. In
proof-of-principle experiments, the
application of angular tunable Fresnel mirrors to the adaptive
autocorrelation and adaptive self-reconstruction was demonstrated. In
analogy to well-known interferometric techniques, the capability of
phase shift approaches to improve the resolution is studied. Specific
transformations of propagating OAM pulses like spatial oscillations of
spectral momenta, temporal aberrations or Guoy effect in sepctral
domain are studied in detail. First experimental results were found to
be consistent with numerical simulations and extend
the
classical theory of polychromatic vortex beams to singular light pulses
with only few (sub-3) oscillations of the electromagnetic field
amplitudes.

Photoluminescence, Second Harmonic Generation
(SHG), Third Harmonic Generation (THG) and Kerr effect of semiconductor
nanolayers and nanorods (ZnO, TiO2) are
studied with sub-3-cycle pulse excitation and single-photon
spectroscopy (together with the group of PD Dr. Steinemeyer). Tailored hybrid nonlinear nanomaterials are used
for plasmon management and localization. The ultrafast dynamics of femtosecond-laser plasmon excitation and
nano-feedback
processes are analyzed. Pump-probe diffraction
experiments are performed with highly sensitive two-dimensional EMCCD
detectors. Preliminary results yield essential contributions to the
understanding of basic
mechanisms of structural changes in materials which are still
controversially discussed in literature. The creation of transient
Drude metals via single and multiphoton excitation is investigated for
semiconducting and dielectric materials (Si, ZnO, TiO2, SiO2).

1991-1998 Society for the Promotion of Applied
Optics, Optoelectronics, Quantum Electronics and Spectroscopy, Berlin,
Leader of the Laboratory for Microoptics and Laser Beam Shaping,
research projects in collaboration with MBI, small and medium
enterprises and Siemens AG, Germany